Antibodies against C1q Are a Valuable Serological Marker for Identification of Systemic Lupus Erythematosus Patients with Active Lupus Nephritis

Abstract

Objective. An early diagnosis of lupus nephritis (LN) has an important clinical implication in guiding treatments of systemic lupus erythematosus (SLE) in clinical settings. In this study, the diagnostic values of circulating autoantibodies to C1q alone or in combination with other markers for accessing active SLE and LN were evaluated. Methods. The diagnostic value of anti-C1q autoantibodies for identification of patients with active SLE disease and LN was evaluated by analyzing the level of anti-C1q antibodies in sera from 95 SLE patients, 40 non-SLE patients, and 34 healthy cohorts. Results. The prevalence of anti-C1q antibodies was significantly higher in patients with SLE (50/95, 52.6%), active SLE (40/51, 78.4%), and LN (30/35, 85.7%) in comparison with non-SLE patient controls, patients with inactive SLE, and non-LN, respectively. A combination of anti-C1q with anti-dsDNA and/or levels of complements C3 and C4 exhibited an increased specificity but a decreased sensitivity for identification of patients with active SLE and LN diseases relative to each of these markers alone. Conclusion. Anti-C1q antibodies were strongly associated with disease activity and LN in SLE patients, suggesting that it may be a reliable serological marker for identification of SLE patients with active LN and active SLE disease.

The Concurrent Anti-C1q and Anti-dsDNA but not Anti-C3b Antibodies as Potent Biomarkers for Lupus Nephritis prediction

“…These data indicated that the evaluation of the simultaneous existence of antibodies against dsDNA and C1q could be useful as diagnostic and predictive biomarkers for SLE patients with kidney involvement. Several studies are consistent with our ndings [5,12,18,20]. Recently, it has been demonstrated that any de ciency in complement activation through classic and alternative pathways strongly correlated with the progression and severity of LN.…”

“…The actual prevalence of antibodies against C1q molecules is controversial in different kidney involvements of patients with SLE. Several studies have addressed antibodies against C1q as a potential biomarker for the prediction of kidney involvement [18][19][20]. However, few investigations revealed the positive serum for anti-C1q directly correlated with only SLE disease activity and it is not speci c for kidney involvement (LN) [21,22].…”

Anti-C1Q Antibodies Concentrations by Elisa in Systemic Lupus Erythematosus

“…This observation supports, but does not confirm, reports that relate high αC1q ab levels to renal symptoms and/or renal flares [18]. There have been many studies over the past two decades of αC1q ab levels in disease, including SLE [17,18]. These, together with this report, suggest that quantitation and standardization of anti-C1q antibodies has a useful role in the classification of subtypes of SLE and as a potential confirmatory diagnostic and monitoring assay [17,18].…”

“…A strong association between αC1q ab and active renal disease has been demonstrated [18]. Only nine studies have longitudinal data permitting this specific assessment (including 10,14), although other reports have supported its potential for this use [9,10,12,17]. The present study measured the levels of αC1q ab in a cohort of diagnosed and treated Western Australian SLE patients using a commercial ELISA kit.…”

“…It has been reported by several groups [6,[8][9][10] that the levels of αC1q ab titers are usually significantly higher in SLE patients than healthy controls or non-SLE autoimmune patients. The concentrations of αC1q ab correlate with disease activity and/or severity [6,[8][9][10][11][12][13][14][15][16][17][18][19] as well as with other laboratory parameters including complement protein C3 and/or C4 concentrations, dsDNA ab, proteinuria and the presence of immune complexes [6,8,11,12,[14][15][16][17][18][19]. Whether serum concentration of αC1q ab is a useful tool to predict up-coming flares in patients with nephritis remains to be confirmed.…”